To be useful as a multipurpose dispersant with wide compatibility in pigmented coating dispersions, the dispersant should be compatible with the acrylic, polyester, alkyd, epoxy resin, polyurethane, and other film-forming resins that are commonly used in surface coating compositions. It should also be able to disperse both organic and inorganic pigments. It should also enhance the tint strength of the pigments, improve gloss, hiding power, and stability of the surface coating composition.
Polymeric dispersants have been known in the art. During coating manufacture, it has been typical to disperse the pigments into only a portion of the total resin vehicle of which the coating composition is comprised, together with appropriate liquid carriers and additives. The resulting dispersion is then mixed with the remainder of the total resin vehicle used in the coating composition. These additions can take place by the ultimate user of the coating composition to adjust color, or they may be used during the actual manufacture of the coating composition itself. However, most pigment dispersions are very specific in their performance and are compatible with only a small number of the diverse solvents and film-forming resins used in coating compositions. A number of polymeric dispersants have been proposed for as multipurpose widely compatible pigment dispersions, but none has proven to be entirely satisfactory. Some do not have the required compatibility with a wide range of the film-forming resins and solvents, or do not have good pigment-wetting characteristics, while others adversely affect the properties of the surface-coating compositions or increase their cost appreciably.
It has now been found that polymeric dispersant resins made from polymerization products of specific monomer units are capable of acting as multipurpose dispersants because they are compatible with a wide range of film-forming resins, as well as capable of dispersing both organic and inorganic pigments. Due to its solvating properties, use of this polymeric dispersant resin reduces the need for solvents typically used for pigment dispersions. Dispersants of this invention can disperse both organic and inorganic pigments wherein the film-forming resin is an acrylic, alkyd, polyester, epoxy resin, polyurethane, or non-aqueous dispersion resin. The dispersants of this invention can also act as a compatibilizer to aid in blending some mutually incompatible polymers (that is, those polymer systems being relatively immiscible and creating a cloudy appearance upon mixing). The dispersants of this invention are useful in pigment dispersions, inks, and surface-coating resin-containing compositions.